OAKLAND -- Nothing should stop Caltrans from opening the new Bay Bridge on Sept. 3 as planned, say two of the three internationally renowned bridge and seismic engineering experts commissioned to review its construction.

The remaining punch-list items -- including the bolt-by-bolt examination that began in March when three dozen anchor rods snapped on the span -- are "minuscule compared to the overall seismic safety of the new bridge," said Frieder Seible, chairman of the Toll Bridge Seismic Safety Peer Review Panel. "There is no reason to keep traffic off the new bridge until after every last bolt has been 100 percent absolutely checked."

"There is every reason to believe (the new bridge) will open by Labor Day," added fellow peer review panelist John Fisher.

The new span of the Bay Bridge on Wednesday, April 17, 2013. (Kristopher Skinner/Staff)

Transportation authorities are still one month and many test results away from a go/no-go decision on the opening. But Seible and Fisher said the critical findings are already in: The bridge relies on the broken bolts only during an earthquake, they said, and even if seismic repairs are incomplete Sept. 3, the new span is far and above the safest option for the 280,000 vehicles that will cross the bridge daily.

Seible and Fisher spoke during a rare and wide-ranging joint interview after their regular construction briefings on the bridge on Friday with engineers and contractors.

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Caltrans created the Toll Bridge Seismic Safety Peer Review Panel in 1997, a cadre of experts tasked with looking over the state's shoulder as it undertook the retrofit and replacement of California's seismically vulnerable spans. The panelists are advisory, but Caltrans usually follows their recommendations.

Seible, who retired last month as dean of the UC San Diego engineering school, has advised Caltrans since 1990. Fisher joined the panel in 2008. The third panelist, geotechnical engineer and UC Davis Professor Emeritus I.M. Idriss, visited the bridge earlier in the week and was unavailable.

But in an environment where the decision to open the $6.4 billion bridge is as much about politics as engineering, whether the experts' reassurances will appease critics is an open question.

With one glitch after another making headlines during the past decade of construction, lawmakers, commuters and even other engineers are asking, "Will this bridge be safe?"

"I have zero confidence in any materials-related decisions as a result of what I've been looking at in the past six weeks," said metallurgist and UC Berkeley materials science professor Tom Devine, who has examined the bridge bolt failure data. "Most of the people telling me, 'Relax, it's fine!' are the same people who were part and parcel of the decisions that caused these problems."

The peer review panelists say they have emphatically delivered their urgent message to the three agencies overseeing the new bridge project.

But Caltrans, the Bay Area Toll Authority and the California Transportation Commission have put off until July 10 a decision about the opening date, citing the unresolved bolt-repair timeline and a pending Federal Highway Administration review.

Meanwhile, state Senate Transportation Committee Chairman Mark DeSaulnier, D-Concord, introduced on Wednesday an emergency bill that would expand the Legislative Analyst's Office study of concrete quality testing on one of the 13 underwater pilings in the large pier east of the tower.

"We will look to the Federal Highway Administration and Caltrans to tell us if the bridge is safe, but we want a review of the process that led to the broken bolts," DeSaulnier said.

No construction glitch in the decade since the work started has been a bigger headache or public relations nightmare than the broken bolts.

In March, 32 of 96 very large -- 3 inches in diameter and 17 to 24 feet long -- high-strength steel anchor rods snapped after contractors tightened them down.

The fasteners are embedded inside two shear keys sandwiched between the bridge deck and the columns on the pier east of the tower. The keys control sway during an earthquake.

The rods cannot be replaced because they are embedded in concrete at one end and there is only 5 feet of headroom where they protrude at their tops. Instead, engineers are abandoning the bolts and retrofitting the shear keys with an external steel cable and saddle system.

A metallurgy team hired to study the failure blames a well-known phenomenon where hydrogen atoms invade spaces between the high-strength steel's molecules when under heavy loads and leave it brittle and subject to fracture.

The team's analysis heightened concerns about the 2,210 high-strength steel bolts installed elsewhere on the span, although none has shown evidence of hydrogen embrittlement. Caltrans is testing the remaining fasteners and more test results are expected in July.

Even if those tests identify additional defective bolts and contractor American Bridge Fluor cannot finish the shear keys retrofit in time, the two peer review panelists say the new bridge should open as soon as the other construction work is completed.

If a moderate temblor were to strike after traffic moves onto the new bridge but before the retrofit is done or any other bolts are replaced, the new bridge is still at least twice as safe as the 77-year-old span motorists use today, Seible and Fisher said.

"The broken bolts are for the shear keys and not the primary load path in the bridge," Seible said. "The bridge will function under traffic perfectly fine without them. In a moderate earthquake, we would see a little bit more damage than we would otherwise see but the bridge will not come down."

Seible and Fisher say they are not worried about the other 2,210 high-strength steel fasteners on the bridge, some of which are integral to the bridge's daily operation. None has shown signs of fracturing, and if ongoing tests should reveal suspect bolts, they can be replaced over time, they said.

But the old bridge sits on vulnerable wood pilings driven into hundreds of feet of soft mud expected to collapse under violent earthquake movements, seismic experts have said for years.

"We have a professional obligation to give our best opinion based on our research and experience," Fisher said. "We owe it to the public and the public's best interest to provide the best state of knowledge we have. It would be immoral to do anything else."

BAY BRIDGE: PEER REVIEW
Caltrans created the Toll Bridge Seismic Safety Peer Review Panel in 1997 to look over their plans to retrofit and replace seismically vulnerable spans.
Critics have questioned the members' independence from a state agency where they have had long affiliations.
But few could dispute the three current panelists' qualifications, which include the engineering profession's highest honor -- membership in the National Academy of Engineering:
Frieder Seible -- Retired UC San Diego engineering school dean. Age 61. Founded seismic lab that tested concrete bridge and roadway column designs Caltrans uses today. Seismic adviser since 1990. Internationally celebrated for seismic safety and blast protection design work on bridges. Appointed in April dean of engineering at Monash, a public university in Melbourne, Australia.
I.M. Idriss -- UC Davis geotechnical engineering professor emeritus. Age 77. Pioneered strategies that public infrastructure builders use to compensate for the way earthquake vibrations move through rocks and soils. Seismic adviser to California since 1990. Private international geotechnical consultant.
John Fisher -- Civil engineering professor emeritus, Lehigh University in Bethlehem, Pa. Age 82. His research formed the basis of many of the industry's steel fatigue prevention failure provisions. Joined peer review panel in 2008. When major steel structures in the world break or collapse, Fisher gets a phone call. Served on the national commission that investigated the collapse of the World Trade Center towers.
-- Lisa Vorderbrueggen